1. Field of the Invention
The present invention relates to a keypad, in particular to a non-backlighted illuminating keypad.
2. Description of Related Art
Backlight module is extensively used as a light source in liquid crystal display, advertising apparatus and portable electronic devices. In a portable electronic device such as cellular phone or personal digital assistant (PDA), the light source is often arranged behind a keypad panel to provide light penetrated through the keypad panel to illuminate the numerals, characters or symbols on the keypad panel.
Conventional backlight module usually includes a light guide plate and a light emitting device (LED) used to emit light into the light guide plate. Light propagates in the light guide plate and diffuses from a surface of light guide plate to keys of the keypad panel, such that users can clearly identify the numerals, character or symbol printed on the surfaces of keys.
Electronic ink techniques are already employed to electronic display apparatus to show information. The electronic ink material includes a plurality of microcapsules each contains both white and black particles in a microcapsule wall. The electronic ink microcapsules are printed on an electrode substrate, which can generate electrical field to control the behaviors of the white and black particles in the microcapsules. By controlling the behaviors of those colored particles in each microcapsule, it is possible to get macroscopic images from the microcapsules printed on the electrode substrate.
Therefore, the electronic ink techniques seem promising to use in a keypad, thus replacing the numerals, characters and symbols printed on the surfaces of keys. However, since the electronic ink material is not transparent, it cannot employ conventional backlight module for illuminating the electronic ink material to display the numerals, characters or symbols and requires an appropriate accompanying light-source module to compose a practical keypad.